PROJECT SUMMARY/ABSTRACT This SBIR proposal is aimed at demonstrating feasibility of developing a technically simple and highly accurate in vitro diagnostic (IVD) assay for Heparin-induced thrombocytopenia (HIT), a serious complication of heparin treatment. The proposed assay is based on recent findings that Platelet Factor 4 (PF4)-treated platelets can be used for the sensitive and specific detection of clinically-significant HIT antibodies. HIT is frequently suspected in heparin-treated hospitalized patients who may have a number of potential causes of thrombocytopenia. To assist with diagnosis and management, physicians rely on two families of HIT assays. The first, the PF4/Polyanion ELISA (PF4 ELISA)-based in vitro diagnostic (IVD) assays are sensitive for the detection of pathogenic, platelet-activating HIT antibodies, but are highly non-specific such that the positive predictive value (PPV) of these assays is poor. The second, more accurate platelet activation-based assays such as the Serotonin release assay (SRA) are technically complex and are performed using radioactivity or HPLC-coupled mass spectrometry at only a small number of reference laboratories. As a result, PF4 ELISAs are used to manage most HIT-suspected patients. Many patients with false-positive ELISAs are inappropriately treated with non-heparin alternative anticoagulants which have a worse bleeding profile than heparin, and unlike heparin, lack an antidote. The goal of Retham Technologies LLC is to revolutionize HIT diagnosis by replacing both the inaccurate ELISA and technically complex SRA with HITDx, a simple yet accurate IVD that can be performed near-patient in the hospital laboratory. HITDx is based on recent groundbreaking research that suggests that pathogenic HIT antibodies can bind to and activate PF4-treated platelets in a heparin- independent manner. Recent studies demonstrate that this technology can be leveraged to provide both early and accurate HIT diagnosis and the USPTO has issued patents related to this technology. This proposal will demonstrate feasibility of developing a self-contained HIT IVD kit using PF4-treated long-term stored platelets. The project will be led by Dr. Gian Visentin, MD, an IVD expert, who, several years back, was key to developing and launching one of the most widely used PF4 ELISAs in the US market. In the proposed studies, he will be supported by Dr. Padmanabhan (lead inventor of the technology), expert consultants and Retham?s advisory board members. Firm commitments from regulatory, quality assurance and business experts for the next phase of development are expected to ensure timely commercialization of this patient-impacting product.